Saya jadi inget Dipo yang memagn sudah gila dan berpengetahuan dangkal kayak
comberan di musim kemarau di Jakarta itu dulu bilang ilmuwan di dekat Jenewa
sono lagi nyari "partikel ketuhanan" karena ada berita yang bilang mereka lagi
nyari God particle...
Kali ini sih ilmuwan lagi bicara tentang "ghost particles".
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BBC News Science & Environment
22 June 2010 Last updated at 11:48 GMT
Neutrino 'ghost particle' sized up by astronomers
By Paul Rincon Science reporter, BBC News
Scientists have made their most accurate measurement yet of the mass of a
mysterious neutrino particle.
Neutrinos are sometimes known as "ghost particles" because they interact so
weakly with other forms of matter.
Previous experiments had shown that neutrinos have a mass, but it was so tiny
that it was very hard to measure.
Using data from the largest ever survey of galaxies, researchers put the mass
of a neutrino at no greater than 0.28 electron volts.
This is less than a billionth of the mass of a single hydrogen atom, the
scientists say.
Their nickname is fitting: a neutrino is capable of passing through a
light-year (about six trillion miles) of lead without hitting a single atom.
The results are to be published in the journal Physical Review Letters and will
be presented at the Weizmann UK conference at University College London (UCL)
this week.
"Back in 2002, we put an upper limit on the neutrino mass of 1.8 electron
volts. So this is an improvement by a factor of six," said co-author Professor
Ofer Lahav, from UCL.
"It is remarkable that the distribution of galaxies on huge scales can tell us
about the mass of the tiny neutrinos."
The work resulted from the PhD thesis of UCL scientist Shaun Thomas, working
with Professor Lahav and Dr Filipe Abdalla.
Scientists used the largest ever 3D map of galaxies in the Universe, based on
data gathered by the Sloan Digital Sky Survey.
Ocean waves
They were able to determine a new upper limit for the neutrino particle by
analysing the distribution of galaxies across the Universe.
The matter in the cosmos naturally forms into "clumps" of galaxy groups and
clusters.
As neutrinos are extremely light they move across the Universe at great speeds.
This has the effect of smoothing out the natural "clumpiness" of matter, the
research team says.
Professor Lahav likens this to ocean waves smoothing out a pile of sand on a
beach.
By analysing the extent to which this "smoothing-out" of galaxies has taken
place, scientists were able to work out the upper limits of neutrino mass.
Professor Lahav believes neutrinos are a minor component of cold dark matter,
the mysterious "stuff" which comprises some 25% of the Universe and more than
80% of matter in the Universe.
"The neutrino is squeezed into that slice [of the Universe] that is dark
matter. But it probably accounts for less than one percent of that dark
matter," he told BBC News.
The neutrino particle comes in three "flavours": muon, tau and electron. In a
recent experiment, physicists caught a neutrino in the act of changing from one
type to another.
The finding by researchers on the Opera experiment in Italy provides a missing
piece in the puzzle that has challenged scientists for decades.
In the 1960s, US scientist Ray Davis observed far fewer neutrinos arriving at
the Earth from the Sun than models predicted. Either the models were wrong, or
something was happening to the neutrinos on their way.
A possible solution to the puzzle was provided in 1969, when theorists
suggested that chameleon-like oscillatory changes between different types of
neutrinos could be responsible for the apparent deficit.
Several experiments have observed the disappearance of muon neutrinos,
confirming the oscillation hypothesis.
But until the results from Opera, no observations of the appearance of a
tau-neutrino in a pure muon-neutrino beam have been observed.
Another project, called Minos, recently reported results which point to a
fundamental difference between neutrinos and their anti-matter counterparts,
known as "anti-neutrinos".
In the experiment, a beam of muon anti-neutrinos was fired from the Fermilab
particle accelerator in Chicago through the Earth to the Soudan underground lab
in Minnesota.
They found a relatively large difference in the way neutrinos and
anti-neutrinos oscillated between one type and another. This difference could
not be explained by the established theory of particle physics, known as the
Standard Model.
paul.rincon-inter...@bbc.co.uk
More Science & Environment stories
Super-Kamiokande detectorParticle 'flips to all flavours'
A Japanese experiment sees hints that neutrino particles can oscillate
between all three types, opening new lines of research to test why matter beat
antimatter at the Big Bang.
Australian dinosaur had UK double
Iron-Age French were beer brewers
BBC
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